Many Christians (nominal or otherwise) have been led to “blame” the Jews for killing Jesus; and it is probably, as you mentioned, partly due to groups or governments looking for a scapegoat. On the other hand - although the first Christians were definitely Jews (how could they be otherwise), it was the Jewish leaders themselves who proclaimed before Pilate, “His blood be on us and on our children!” Of course, according to Mosaic law, the children were not to be punished for their parents’ guilt (a common practice in many cultures of the day).

I think one reason that makes anti-Semitism so easily accepted by many people is that the Jews look after their own, and as a result, most Jews are very successful, generating a great deal of envy. So many people are ready to “blame” them for all their own misfortunes.